With the development of display technologies, flat panel display devices, because of the advantages of high definition, power saving, body thinness, wide application scope, and the like, are widely applied to various consumer electronic products such as mobile phones, televisions, personal digital assistants, digital cameras, notebook computers, and desktop computers, and become mainstream display devices.
Organic light-emitting display devices have the features of self-illumination, high brightness, wide viewing angle, high contrast, flexibility, low energy consumption, and the like, and thus have attracted wide attention. As a new generation of display mode, the organic light-emitting display devices have begun to gradually replace traditional liquid crystal display devices, and are widely applied to electronic products such as mobile phone screens, computer monitors, and full-color televisions.
Compared with a display mode of a traditional liquid crystal display (LCD), the display technology of organic light-emitting diode (OLED) uses extra-thin organic material coatings and glass substrates without any backlights, and when a current flows through organic materials, these organic materials will emit light.
An active-matrix (AM) flat panel display device, a most commonly used display device currently, which controls input of data signals through a thin film transistor (TFT) switch, and thereby further controls display of images.
An existing thin film transistor-liquid crystal display (TFT-LCD) mainly comprises two glass substrates and a liquid crystal layer, wherein a surface of an upper glass substrate is provided with a color filter, and a lower glass substrate is provided with a thin film transistor and a pixel electrode. The color filter includes color photoresist and a black matrix. A position of the color photoresist corresponds to a position of the pixel electrode. The black matrix is formed among the color photoresist. In general, the black matrix is subject to the steps of coating, exposure, and development to form the surface of the upper glass substrate.
The aforementioned black matrix is indispensable in the color filter of the existing TFT-LCD. For a vertical alignment TFT-LCD, a liquid crystal, because of being in vertical state in the absence of electric field control, blocks light, so that an overall picture is rendered completely black at this moment, and no light leakage occurs. However, in the case that the pixel electrode is driven by a voltage, a liquid crystal angle on a metallic circuit connected with the pixel electrode will be changed because of transmittance of voltage signals, and thereby a light leakage problem is generated. Therefore, the black matrix is adopted for correspondingly shielding the metallic circuit around the pixel electrode so as to avoid the light leakage problem.
With the rapid development of the inkjet printing technology, more and more manufacturers manufacture OLED and organic light-emitting display devices by using the inkjet printing technology.
Inkjet printing (IJP), as a new method for manufacturing an organic layer of an Active Matrix-Organic Light-Emitting Diode (AM-OLED), has the features of high efficiency, low cost, and the like, and thus is paid much attention to by manufacturers.
In the process of manufacturing an AM-OLED by using IJP, a bank layer is required for defining a light-emitting area, but due to the hydrophilicity-hydrophobicity problem of bank materials, an organic layer manufactured through IJP will have a problem of thick edge warping.
A simple structure of an OLED device based on the inkjet printing technology in the prior art is shown in FIG. 1, and the AM-OLED includes a base 10, bank layers 11 provided on the base 10, and an organic light-emitting layer 12 disposed between the bank layers 11.
A first key step of inkjet printing is to process the bank layer 11 into a layer with surface hydrophobicity, and a second key step of inkjet printing is to jet OLED ink to a groove formed by the bank layer 11. Because most of OLED ink is hydrophilic, when the OLED ink is jetted to a bank material, due to the poor contact force of hydrophobic and hydrophilic materials, the OLED ink will roll into a groove formed by the bank layer 140. However, because a contact angle between the ink and the groove will directly affect the uniformity of the ink in the groove, when the OLED ink is jetted and the contact angle between the ink and the groove is improperly controlled (for example, the contact angle is greater than 90 degrees), the disadvantages of poor contact between an ITO base and an OLED material, existence of a clearance between the groove and the OLED material, and inhomogeneous distribution of the OLED material in a manner that a middle is thicker than two sides are caused, which is unfavorable for uniform light emission.
As shown in the figures, a situation that a surface of the organic light-emitting layer 12 is non-uniform will occur due to the edge warping of the organic light-emitting layer 12 in the AM-OLED, and the situation will eventually cause a problem of non-uniform light emission.
Current solutions focus on improvement of the uniformity through a procedure, such as adjustment of the hydrophobicity-hydrophilicity of the bank, but the method has a potential matching problem the bank and the ink, and thus has not been universally adopted.